The potential for inappropriate ventricular tachycardia confirmation usingthe Intracardiac Electrogram (EGM) Width Criterion

The "Intracardiac Electrogram (EGM) Width Criterion," the first digital sig nal processing feature used in an implantable cardioverter defibrillator (I CD), is a detection enhancement algorithm that intends to improve ventricul ar tachycardia (VT) defection specificity by rejecting inappropriately dete cted supraventricular tachyarrhythmias. The algorithm may be activated afte r setting the optimal EGM source, slew, and width thresholds based on EGM w idth testing during sinus rhythm. This study evaluates the accuracy of the EGM width measurements during exercise testing. Twenty-one patients with Me dtronic Micro Jewel II Model 7223 ICDs underwent treadmill exercise testing . EGM width resting was repeatedly performed during exercise and recovery t o detect potential inappropriate measurements. In seven (33%) patients the EGM Width Criterion inappropriately confirmed VT detection. Eleven patients had inappropriately wide EGM width measurements, but did not satisfy the E GM Width Criterion. The causes of wide EGM width measurements were an actua l increase in EGM width and/or inappropriate detection of the baseline irre gularities as EGM onset or offset points. Based on our observations, we rec ommend to test the EGM Width Criterion during exercise testing for optimal ICD programming.